The Tissue Level Flashcards
What is a tissue?
a group of cells with a common embryological origin that function together to do specialized activities
What is histology?
the science that study the tissues
What are the tissues of the body?
epithelial, connective, muscular, nervous
How do the cells within tissues remain anchored to other cells or structures?
by points of contact called cell junctions
What are the types of cell junctions?
tight, adherens, desmosomes, hemidesmosomes, gap
What are tight junctions?
web-like strands of transmembrane proteins that fuse adjacent membranes, it prevents the passage of substances between the cells
What is an adherens junction?
transmembrane proteins and microfilaments form a dense layer of protein on the inside of the membrane called the plaque, resists separation of cells during contractile activites
What connects the plaques in an adherens junction, what does it form?
glycoproteins called cadherins on both cells connect the plaques and from the adhesion belt
What are desmosomes?
similar to adherens junctions but the plaque does not attach to microfilaments, the plaque attaches to the intermediate filaments, weld-like
What is the strongest cell junction?
desmosomes, weld like junctions are the strongest and prevent cells separation under tension during contraction
What are hemidesmosomes?
half a desmosome, glycoproteins are integrins not cadherins, they anchor cells to the basement membrane, not to each other
What are gap junctions?
the plasma membranes are not fused (there is a gap in between), connexin proteins form fluid-filled channels in between the cells called connexeons
What are connexons?
connexin proteins forming a fluid filled channel between cells in gap junctions
What do gap junctions allow?
for physical intercellular communications
What is epithelial tissue?
the covering and lining tissues for surfaces, cavities, and ducts, also forms glands
What are the general features of epithelial tissue?
densely packed and arranged in sheets, many cell junctions, mitosis occurs frequently, attach to and supported by a basement membrane, is avascular but it does have a nerve supply, selective barrier, provide protective and secretory surfaces for the body, combine with nervous tissue to form special organs
What special organs can be formed when epithelial tissues combine with nervous tissue?
smell, hearing, vision, touch
What is an apical surface?
epithelial tissues always have this free surface that may contain cilia
What is a basal surface?
on epithelial tissue that is adhered to a basement membrane
What is a basement membrane?
a thin extracellular layer composed of basal lamina and reticular lamina.
What is the basal lamina of the basement membrane?
part of the hemidesmosome, made of proteins secreted by epithelial cells: laminin, collagen
What is the reticular lamina of the basement membrane?
made of collagen secreted by the fibroblasts of the connective tissue underneath
What are the functions of the basement membrane?
attaches and supports the overlying cells, provides surface for cell migration in growing and healing, restrict the passage of large molecules (filtration of blood in kidneys)
True or false: epithelial tissue has its own blood supply that supports the connective tissue underneath
False: has no blood supply, requires support from the connective tissue underneath
